XMLHttpRequest: readystatechange event

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

Note: This feature is available in Web Workers, except for Service Workers.

The readystatechange event is fired whenever the readyState property of the XMLHttpRequest changes.

Warning: This should not be used with synchronous requests and must not be used from native code.

Syntax

Use the event name in methods like addEventListener(), or set an event handler property.

js
addEventListener("readystatechange", (event) => {});

onreadystatechange = (event) => {};

Event type

A generic Event with no added properties.

Examples

js
const xhr = new XMLHttpRequest();
const method = "GET";
const url = "https://developer.mozilla.org/";

xhr.open(method, url, true);
xhr.onreadystatechange = () => {
  // In local files, status is 0 upon success in Mozilla Firefox
  if (xhr.readyState === XMLHttpRequest.DONE) {
    const status = xhr.status;
    if (status === 0 || (status >= 200 && status < 400)) {
      // The request has been completed successfully
      console.log(xhr.responseText);
    } else {
      // Oh no! There has been an error with the request!
    }
  }
};
xhr.send();

Specifications

Specification
XMLHttpRequest Standard
# event-xhr-readystatechange
XMLHttpRequest Standard
# handler-xhr-onreadystatechange

Browser compatibility

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